Printers are constantly being pushed to perform more tasks locally, provide better print quality, and operate at higher printing speeds. Today's printers have far greater print head scan rates and fire far more dots within each scan than their predecessors. These requirements increase the amount of data being handled within the printer within an increasingly shorter time frame. With print head technology advances, it is not uncommon for a single print head to have 1200 nozzles, which enables better resolution and print quality.
Conventionally, one bit of print data is required to fire each corresponding nozzle. Accordingly, for a 1200-nozzle print head, 1200 bits of data are required to fire (or not fire) all 1200 nozzles. Suppose the pen is operated at 100 kHz. For this rate, the printer needs to send 1200 bits of data every 10 .mu.s. This yields a whopping data rate of 120 Mb/sec. Now, suppose the printer has more than one pen. For a common four-pen system, the data rate becomes 480 Mb/sec. Unfortunately, data bandwidth is not infinite and such high data rates are practically unavailable at this time.
Current print head technology implements firing logic on the print head. The firing logic is formed into the silicon wafer that forms the nozzles and the heated firing elements. This reduces the number of connections to the pen and allows the print head to decode data at least partially on the fly. The firing logic still requires, however, the one data bit per nozzle ratio. As a result, the current pen technology effectively worsens the data rate problem.
Accordingly, there is a need for a new approach to driving high quality pens without exceeding practical data rates.
A countervailing concern is the ever present pressure to lower the cost of printers. The marketplace continues to drive printer prices down and thus, any solution to the data throughput problem must be cost sensitive.